interhg: allow more flexible pattern specification (fixes 2/3 of issue699) - something else than "pat" followed by a number can be used as key - something else than "/" can be used as delimiter - "ilmsux" flags (e.g. "i" for case insensitive) can be used

#!/bin/sh

hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'

hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'

hg debugrename foo
hg debugindex .hg/store/data/bar.i